Technical Field of the Invention
The present invention relates generally to an automatic film washout system used in forming an etching stencil from a photosensitive material, and more specifically to an automatic film washout system using an unique pressurized water delivery system with a booster pump assembly to greatly reduce water usage using high pressure to replace conventional high water usage of lower pressure systems. This allows the unit to now operate with no on board water storage buffer storage tank used to supply washout cycle water at a higher rate than inlet supply.
Description of the Related Art
Sandblast etching, carving, and engraving highly detailed designs in materials, such as glass, crystal, stone, and metals is well known in the art. In order to produce such highly detailed designs, stencil-like overlays are commonly employed as a tool to facilitate formation of the detailed design within the material. In this regard, when the stencil is laid upon the base material, the stencil may define openings corresponding to the areas of the base material that are to be etched or carved, and cover the areas of the base material that are not intended to be etched or carved.
The stencils are typically formed from a sheet of photosensitive material that is exposed to light corresponding to the design or pattern that is to be etched or carved into the base material. After exposure to the light, the photosensitive material is developed, and uncured emulsion is removed from the stencil to define the openings in the stencil.
The uncured emulsion may be removed from the stencil through a rinsing or washout procedure wherein liquid is directed onto the stencil. Several prior art devices have been developed to perform the washout procedure, and typically include a rotating drum upon which the photosensitive material is mounted for rinsing. A water delivery system sprays pressurized water on the stencil for rinsing the emulsion therefrom. The water delivery system typically includes a pump and a plurality of spray nozzles fluidly connected to the pump. The pumps in many conventional washout devices are configured to pump water at 4.3-8.3 gallons per minute, which is typically higher than the flow rate of most municipal water lines. Thus, a water buffer holding tank is required to store enough water to supply enough water so as to satisfy the pumping capacity of such pumps.
The holding tank is relatively large and typically includes a heating element to heat the water within the holding tank to a preferred rinsing temperature. The holding tank is generally open to the atmosphere, and thus, washout units having such open-to-the-atmosphere tanks will be referred to herein as “open-to-the-atmosphere” units.
Although such open-to-the-atmosphere units may effectively remove the emulsion from the stencil, they suffer from several deficiencies. One significant drawback to open-to-the-atmosphere units is that they operate at a lower pressure than this new design. While the pump increases the pressure of the water before the water is sprayed onto the stencil, the pressure of the water immediately upstream of the pump is approximately equal to atmospheric pressure (since the holding tank is open-to-the-atmosphere). Thus, the pressure increase created by the pump is inhibited by the low pressure of the water in the holding tank. In order to compensate for the low operating pressure, the conventional washout devices typically operate at a high flow rate of water. This significant increase in water, normally more than inlet supply, requires water storage on board the unit. The new design using the enclosed booster pump with pressurized design cleans faster with higher pressure using less water and does not require any on board water storage supply. Older open to atmosphere units using lower washout pressure require much higher water usage and still produced longer washout times. This longer washout time using increased water amounts can damage film with a wide range of film detail ranging from bold open areas to fine detailed lines on the same part. The new design using low water flow, less time and higher pressure helps to eliminate this washout damage.
Other drawbacks associated with the open-to-atmosphere units includes poor insulation coverage, which results in the loss of heat from water in the holding tank. Furthermore, the tanks generally lack provisions for protecting against tank overflow or spillage.
Another deficiency commonly associated with many conventional non-automatic washout systems is that they are manually operated. In this regard, such manually operated systems typically require that an operator remains with the system during washout operations, i.e., the operator cannot walk away from the system during washout. The labor costs associated with manual operation of conventional washout systems tends to increase the overall cost of the washout procedures. Furthermore, manual operation tends to also include inherent human error.
Therefore, there is a need in the art for an improved automatic washout system that allows for higher water pressure and less water usage during the washout of a stencil to help lesson damage to the film with film over and under washout. Various aspects of the present invention address these particular needs, as will be discussed in more detail below.